412 Prof. M'Intosh on the 



absence from the surface is no proof that they are not in the 

 lower regions of the water. Rough or, in winter, cold 

 weather generally causes even adult pelagic forms to seek the 

 lower regions of the water, and it is unlikely that delicate 

 larva? would be less sensitive. If in temperate regions it should 

 happen that these mild, calm days were frequent throughout 

 the year, such organisms would appear in the surface-waters 

 during a considerable part of the year, if not throughout it, 

 since from January to December pelagic larval forms (ben- 

 thonic) of one kind or other are present. It is true the 

 numbers of such forms would constitute a spindle with tlie 

 bulky region in the warmer months, but, nevertheless, a con- 

 siderable number occur in what are called the colder months. 



It is thus doubtful how far we can accept tliis theory, viz., 

 that the '' cooling at the poles killed off the animals with 

 pelagic larvai or forced them to migrate to the warmer 

 troj)ics." Considerably stronger evidence is yet required 

 before we can assert that towards the poles deep-sea animals 

 have no pelagic larva?. 



In surveying the tidal fauna of the Channel Islands, such 

 as Guernsey, Herm, and Sark, one of the most prominent 

 features is tlie abundance of the Protozoan Noctiluca, which 

 here and in the south of England causes the sea to be bril- 

 liantly phosphorescent, whereas, so far as known, it never 

 occurs in the northern part of Britain, the phosphorescent Cera- 

 tium there taking its place. The ravages of the boring-sponge 

 [Hymeniacidon celata) are everywhere visible in the oyster- 

 beds in the inshore waters, and especially in the beautiful 

 arborescent patterns in many of the dead bivalves and limpets 

 on the shell-beach at Herm. The same form affects the 

 calcareous rocks on the southern shores of England. 



Of zoophytes the most noteworthy are Aglaophenia pluma 

 and A. ^^emiatida, and the presence of Tubular ia indivisa 

 in the Gonliot Caves of Sark at low water. Yet we have 

 seen that this likev/ise occurs occasionally in Shetland. 



Between tide-marks the gaudily-striped Sag artia parasitica 

 is carried about on shells inhabited by hermit-crabs, while in 

 the deeper water the richly-tinted Adamsia palliata is common 

 on shells inhabited by Eupagurus Prideauxii. 



liosy feather-stars are frequent between tide-marks, as are 

 also fine examples of the bluish or purplish Asterias glacialis, 

 and in the adjoining area are the purple, Flemings's, and the 

 silky-spined urchins, together with Synapta Oallienni. In 

 no other area is there such a combination. 



In the same way richly-coloured Planarians like Eurylepta 

 vitiata, and ^emerteans such as Borlusia Elisabethce^ Drepa- 



